A substantial difficulty experienced with capacitance probes is the invasion of the process fluid into the gland housing. The fluid, forced under the process pressure, shunts the electrical capacitance circuits, causing anomalies in detected values. This tendency of the fluid to invade the gland housing is accentuated by repeated temperature cyling of the assembly which, because of the differences in thermal coefficients of expansion of the probe components, rapidly destroys the assembly seals. In my prior patents, U.S. Pat Nos. 4,054,744 and 4,137,558, I disclose and claim an improved probe and sealing gland construction which provides for a continuous insulation coating of the probe which has an intermediate portion with non-coincident sidewall surfaces received within a cavity of the gland housing. This construction provides axial and rotational restraint of the probe rod without clamping rings and the like which require interruption of the insulation coating. In practice, it has been found that this particular construction has a markedly improved service life under thermal cycling conditions, presumably because the non-coincident sidewall intermediate portion flexes sufficiently to accommodate differential rates of expansion of the probe elements. The particular construction of the probe gland housing illustrated in the aforecited patents is costly and, furthermore, is adaptable only to the smaller diameter probe rods which can be readily bent into the illustrated arched configuration.